<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // 求n~m的累加和
        function getSum(n = 0, m = 0) {
            let sum = 0
            for (let index = n; index <= m; index++) {
                sum += index
            }
            // console.log(sum);
            document.write(`输入的参数累加和：${sum}`)

        }

        // 弹框输入起始值和结束值
        let num1 = +prompt('请输入起始值：')
        let num2 = +prompt('请输入结束值：')

        getSum(num1, num2)
    </script>
</body>

</html>